By: Cheyenne Cheung

Diatoms and Photosynthesis  Photosynthetic micro-organisms— autotrophic  Contain chlorophyll that are yellowish in color  An important source of food for marine organisms because they are photosynthetic Chloroplasts

Structure of Diatoms  Single-celled with intricate skeletons  Bilateral symmetry, radial symmetry or asymmetrical  Shells made of silica with a layer of organic material  Skeleton called ‘frustule’

 Some are motile  Along the raphe (slit alongside cell) there are tiny microfibrils that help diatoms move  Can be found in long chains or colonies  Have both freshwater and marine habitats Chain Colony

Symmetry  Centrate diatoms generally have radial symmetry  Pennate diatoms typically have bilateral symmetry  Both found in either fresh or salt water Radial symmetry Bilateral symmetry

Did You Know?  Diatoms are responsible for 20-25% of all organic carbon fixation on the planet  Fossilized rocks composed of diatoms, known as diatomaceous earth, are commercially mined as abrasives or filtering aids  Diatoms are a major component of plankton  Many toothpastes contain diatom skeletons

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Review 1. What are diatom shells composed of? 2. How do diatoms get their food? 3. What kinds of symmetry do diatoms have? 4. What is the skeleton called? 5. Are diatoms motile? 6. What percentage of organic CO2 fixation are diatoms responsible for? Answers: 1. silica 2. photosynthesis 3. bilateral, radial, asymmetrical 4. frustule 5. yes %

Bibliography Pictures    atoms_MC_.jpg   tml Information     uk.org.uk/mag/wimsmall/diadr.html